State machines built from integrated circuits need to be radiation hardened to prevent soft errors that occur when a high energy particle travels through the integrated circuit's semiconductor substrate. This is particularly important when the state machine operates in high radiation environments such as outer space. An ionizing particle traveling through the semiconductor substrate may cause a transient voltage glitch, i.e., a single event transient (SET), or may cause a sequential state element to store the wrong state, i.e., a single event upset (SEU).
One technique for mitigating such effects of high energy radiation is to provide a self-correcting triple-mode redundant (TMR) circuit. In this manner, if a radiation strike results in a soft error in one copy of the circuit, the other two copies of the circuit can correct the soft error in the affected copy of the circuit through self-correction techniques. However, charge collection can affect clocking circuitry and in particular can cause a single event transient (SET) in the global clock signal. This can cause sampling at incorrect times thereby defeating the self-correcting mechanism of the redundancy. Therefore radiation hardening techniques are needed for clock signals as well as storage elements. Additionally, SETs may affect the state element inputs.